D2community

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Unformatted text preview: Community Ecology Biodiversity • Levels of biological diversity Community Ecology part 2: Biodiversity Two communities can have the same species richness, but a different relative abundance Biodiversity A B • Species richness = # species/area • Relative abundance = proportion of total diversity taken up by a few dominant species • Òspecies richness + Úrelative abundances Òbiodiversity stability • A community with an even species abundance is more diverse than one in which one or two species are abundant and the remainder rare Figure 54.9 N.Am. bird species diversity Estimating Community Diversity • Shannon Diversity Index (H) D A: 25% Community 1 B: 25% C: 25% D: 25% A: 80% Community 2 B: 5% C: 5% D: 10% Estimating Community Diversity • Shannon Diversity Index A B A: (0.25 x ln 0.25) B: (0.25 x ln 0.25) C: (0.25 x ln 0.25) D: (0.25 x ln 0.25) -----------------------∑ = 1.39 = H C D A: 25% A: 80% Heyer C Community 1 B: 25% C: 25% Community 2 B: 5% C: 5% D: 25% A: (0.80 x ln 0.80) B: (0.05 x ln 0.05) C: (0.05 x ln 0.05) D: (0.10 x ln 0.10) -----------------------∑ = 0.71 = H D: 10% 10 Community Ecology In addition to habitat complexity, Dominant Species other major factors related to community diversity: • Climate • Vegetation with the highest density and/or biomass – especially water availability 180 200 140 Vertebrate species richness (log scale) Tree species richness 160 100 120 100 80 60 40 20 10 1 0 100 (a) Trees redwoods 50 500 700 300 Actual evapotranspiration (mm/yr) 900 500 1,100 (b) Vertebrates 1,000 1,500 2,000 Potential evapotranspiration (mm/yr) Figure 53.25 In addition t...
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